The rules for path tracing are:

The procedure constructs paths from the eye to a light source using bidirectional path tracing, then constructs slight modifications to the path.

In path tracing, however, only a single ray or none is fired at each intersection, utilizing the statistical nature of Monte Carlo experiments.

Well known algorithms for computing global illumination include path tracing, photon mapping and radiosity.

In order to get high quality images from path tracing, a large number of rays must be traced to avoid visible noisy artifacts.

A decade later, Lafortune suggested many refinements, including bidirectional path tracing.

It meant accessing the camera-web and doing some path tracing.

Methods that trace rays, but include additional techniques (photon mapping, path tracing), give far more accurate simulation of real-world lighting.

This flexibility enables bidirectional path tracing, Metropolis light transport, and many other rendering algorithms that cannot be implemented with tail recursion.

Another approach using Monte Carlo methods has led to many different algorithms including path tracing, photon mapping, and Metropolis light transport, among others.